Yeah it will need an insert welded in. I was going to stop by Metal Supermarket today but my Jeep Cherokee blew an upper rad hose when I was on the other side of the city so the plans changed. I lost most of the coolant but it seems to have survived. Design defect I am sure.
So the mold will be 3d printed using PETG plastic, which might take the abuse of being a forming buck for the radiused holes. That you could then tack into a housing. You would need to go slow. Pretty sure I will make the housing mold without the holes. Then make another mold to make the holes. Then epoxy them together. Just easier to print the mold. Once I draw the holes, I will print one at 100% fill. Strongest setting. It might survive using a shop press to stamp a radiused hole.
That would work well if you didn't want it to look like an original 70-71 340 air cleaner. The radius is about the same, but the sides of the opening are square instead of round. I plan on practicing a lot on scrap sheet metal in order to get the holes in post #23 to look like the holes in post #6. It's going to require an inside die of some sort to be placed on the backside of the metal and then worked into shape from the front.
A light bulb popped on in my head when I read your reply! Making the oval openings slightly larger could serve 3 purposes. 1- It would alleviate having to repair or replace the metal in the opening where you remove the existing snorkel. Simply make it just big enough to use existing metal to roll an inward lip. Replicate it on the passenger side of the air cleaner, and done! 2- It would really be unnoticeable at a casual glance, but would be pretty obvious to someone requiring an original 70-71 340 air cleaner. 3- Better air flow for a 408/416 disguised as a 340 in a stock looing car!
